Semiconductor chips such as semiconductor memories may be stacked from a viewpoint of high functionality, high integration, and the like. A penetrating electrode called a through-silicon via (TSV) is used to electrically connect elements between the plurality of stacked semiconductor chips. The TSV penetrates through a semiconductor chip and is electrically connected to elements of other semiconductor chips.
The TSV is formed from the rear surface side of the semiconductor substrate after a semiconductor element is formed on a front surface side of the semiconductor substrate. In this case, in a lithography process, positional alignment needs to be performed from the rear surface side of the semiconductor substrate. Infrared light (IR) is used in order to visualize an alignment mark through the semiconductor substrate from the rear surface side of the semiconductor substrate.